“I warn people before filming, I am going to mess up,” the Oscar-winning star says.

She’s been “sloppy” ever since studying at the Neighborhood Playhouse in New York in the 1960s with Sanford Meisner, who emphasized a natural style. “The main thing that Sanford Meisner gave me — not really just for acting but life — is just be in the moment,” she says.

In director Rob Reiner’s “And So It Goes,” which opened July 25, Keaton plays Leah, a widow attempting a second start in life as a lounge singer. The problem is, she gets so emotional performing songs that she rarely makes it through a whole set. Her curmudgeonly neighbor, a widower named Oren (played by Michael Douglas), drives everyone in their four-plex crazy. Opposites, naturally, attract.

“And So It Goes” marks the first time that Keaton, 68, has worked with Douglas and Reiner, although she auditioned for a long-forgotten 1971 youth drama, “Summertree,” that starred Douglas, with Reiner playing his best friend. She didn’t get the gig.

Keaton says she is happy to be working with Douglas at this point in their careers. “In a way, for me, he’s never been more attractive,” Keaton says. “He’s really grown into himself.”

Aging, or more precisely, aging well, is a topic on Keaton’s mind these days. Her new book, “Let’s Just Say It Wasn’t Pretty,” deals with the possibilities and problems of getting older.

Keaton wrote the book because she thought it would be interesting “to do a group of essays on subjects that really concern women at basically my age and a little younger, and what they go through and how sometimes what appears to be wrong turns out to be right for a lot of us.”

Sitting at a corner table in a Santa Monica restaurant, she is dressed in her quintessential attire: black hat; tinted glasses; black skirt; a crisp, white, long-sleeve blouse; and a black jacket tightly cinched by a large black belt. The fashionista, director, photographer and famed house flipper is funny, honest and endearing during the conversation — and surprisingly down-to-earth.

That’s exactly how she comes across in “Let’s Just Say It Wasn’t Pretty,” where she discusses her insecurities (she once wore a bobby pin on her nose to fix its shape); raising her two children — Dexter, 18, and Duke, 13; her obsession with flipping homes; and her fashion icons, including Cary Grant and Katharine Hepburn.

She notes that, in her family, she and her sisters were insecure. “I think women are, in general,” she says, “especially about appearance and how we handle ourselves in the world. I was just writing to people like-minded who have these issues.”

In the book, Keaton relates how she was in the running for the 1971 romantic NBC detective series “McMillan & Wife,” starring Rock Hudson, for the role of his young wife. But they weren’t thrilled with her eyes. “The eyes go down,” she says. “They tried to get them up.”

That role went to Susan Saint James. Shortly after, Keaton was cast as Kay in Francis Ford Coppola’s landmark 1972 Oscar-winner, “The Godfather.” A few years later, Keaton earned a lead actress Oscar and became a fashion icon in Woody Allen’s 1977 best-picture masterpiece, “Annie Hall.”

Losing “McMillan & Wife,” Keaton says with a wide smile, “turned out to be OK.” (And she never fixed her eyes.)

The men in her life — Warren Beatty, with whom she appeared in 1981’s “Reds,” her “Godfather” trilogy leading man Al Pacino and especially Allen — also are a big part of the book.

She met Allen when he cast her in 1969 in the Broadway production of “Play It Again, Sam.” “I had a crush on him right from the beginning,” says Keaton, who reprised her role for the 1972 film version. “He was perfect for me.”

Besides “Annie Hall” and “Play It Again, Sam,” they worked together on several more films, including “Sleeper” (1973) and “Manhattan” (1979). She remains very close to Allen. Earlier this year, she accepted the Cecil B. DeMille Award at the Golden Globes for the notoriously awards-phobic filmmaker.

WASHINGTON – Hillary Clinton challenged Congress on Thursday to combat fake and misleading news on social media, using a post-election appearance to tackle an issue that gripped her presidential campaign and culminated with a shooting incident Sunday in Northwest Washington.